Venous access catheters provide venous access to the central circulatory system. Venous access catheters include central venous catheters, dialysis catheters and peripherally inserted central catheters, also known as PICC lines. The access line is used for the delivery of intravenous fluids, medications such as chemotherapy drugs and antibiotics, and blood products. Venous access catheters may also be used as access mechanisms for blood sampling and the administration of contrast agents during diagnostic Computer Tomography (CT) procedures.
One type of venous access catheters, PICC lines, provide venous access to the central circulatory system through a peripheral vein. PICC lines have been in use for many years with a variety of configurations. These include single lumen, dual lumen and other multi-lumen configurations. They come in various lengths to accommodate different anatomy and catheter insertion sites. Generally, a PICC line is inserted through a peripheral location such as the arm, with the tip placed in the central circulation, such as the superior vena cava. The PICC line is designed to remain within the patient for a period of one week to a year and can be accessed in an inpatient, outpatient or home setting.
The majority of the PICC lines presently on the market are made from single material such as silicone rubber or polyurethane. While these catheters are biocompatible and designed to minimize indwelling side effects and optimize patient comfort, they do have several drawbacks. The soft material characteristics of the catheter provide patient comfort but increase insertion difficulties and reduce the long-term durability of the catheter. The material characteristics of the catheter shaft also restrict use to only low pressure injections, typically less than 100 psi.
The PICC line should be sufficiently flexible so that it minimizes patient discomfort and does not cause trauma to the vein wall during insertion or over prolonged periods. On the other hand, it should be rigid enough to facilitate insertion over a guidewire. Pushability and resistance to kinking during and after insertion require a stiffer shaft material. These opposing technical requirements have been partially addressed by some manufacturers by incorporating a softer tip welded to the catheter shaft. While this design provides a soft, atraumatic distal end allowing a stiffer, more rigid shaft body, the catheter is uncomfortable to the patient because the majority of the shaft is stiff. In addition, the physician cannot customize the length of these catheters by cutting at the tip, as is commonly done in the practice.
The PICC line is inserted percutaneously, either under fluoroscopic guidance or using a bedside, “blind” approach followed by x-ray imaging to confirm correct tip placement within the vessel. With either technique, the medical professional must confirm that the distal tip of the PICC line is located within the superior vena cava, rather than in the jugular vein or other unintended vessel. Typically, a post-placement x-ray is used to visualize the distal segment of the catheter within the body. Most venous access catheters do not have sufficient radiopacity to allow for easy visualization of the distal tip.
Some venous access catheter designs have attempted to address this problem by providing a highly radiopaque distal tip bonded to the shaft. The drawback of this enhanced tip design is that it prevents the physician from cutting the tip to customize the length of the PICC line. The design also requires a bond or weld joint, which decreases the overall strength of the catheter and increases the risk of fracture at the bond or weld point.
Other catheter designs have attempted to provide acceptable distal radiopacity levels by using highly filled polymer throughout the entire shaft length. Although providing an acceptable level of visibility, the highly filled shaft material had poor fatigue and chemical resistance, which resulted in an increased occurrence of shaft fracture due to external exposure conditions. The shaft is subject to failure at the proximal end where the catheter exits the body. At the point at which the catheter shaft exits the patient's body, the catheter is exposed to extensive bending, manipulation, and surface contact with site care chemicals such as antibiotics and antiseptics.
Some PICC line designs include a separate obturator or other type stiffener device to provide additional stiffness during insertion. Once inserted and positioned, the obturator is removed from the lumen of the PICC line. While this design has the advantage of ease of insertion, the shaft is soft and not radially strong enough to handle the internal pressures associated with CT injections. In addition, for multi-lumen PICC lines, the medical professional must be cognizant of which lumen to insert the obturator into as incorrect insertion may damage the catheter.
Most PICC lines have a capability of withstanding less than 100 pounds per square inch (psi). This is particularly true of silicone-based PICC lines. Although most PICC line pressure capabilities are sufficient for the delivery of medications and for sampling of blood, they are not designed for delivery of contrast media using a power injector. Power injectors are used in radiology suites as a method for rapidly delivering diagnostic contrast media, particularly for CT applications. Contrast media delivered using a power injector can reach injection pressures of almost 300 psi. Although an in-place PICC line provides an available delivery path for the contrast media, it often cannot be used because the PICC line cannot withstand the higher pressures generated when using a power injector. Instead, the physician must access the patient's vein in another location using a short IV-type catheter designed to withstand higher pressures.
Patients with PICC lines are often very ill and gaining access to a vein is difficult for the caregiver on the one hand while it is as painful and traumatic for the patient on the other hand. Continuous access of the venous system by IV needles or catheters results in eventual destruction of the available veins. Accordingly, being able to access the venous system using an already-in-place PICC line would have significant advantages to both the patient and the health care providers.
Therefore, it is desirable to provide a variable-characteristic venous access catheter that is sufficiently rigid for ease of placement and yet sufficient flexible so as not to damage vessels.
It is also desirable to provide a venous access catheter that is comfortable to the patient and also have sufficient durability including chemical and fatigue resistance to withstand prolonged indwelling times.
It is further desirable to provide a venous access catheter that can withstand higher-pressure injections generated by power infusion devices without causing catheter damage.
It is also desirable to provide a venous access catheter that is designed as a one-piece construction for enhanced reliability and strength.
It is further desirable to provide a venous access catheter with a distal segment having enhanced visibility under X-Ray or fluoroscopy to aid in placement without compromising overall catheter strength.